液膜密封振动及冲击动力学特性

液膜密封运行过程因工况瞬时变化、系统振动及润滑不足等因素易引发端面接触冲击,严重影响密封寿命。建立考虑端面接触的液膜密封动力学模型,采用直接数值求解方法对运动方程、质量守恒空化边界雷诺方程、微凸体接触方程在全时间域内耦合求解,研究了液膜空化、轴向扰动及运行工况瞬变对密封稳定性与冲击特性的影响。结果表明:液膜空化有效提高了系统抗干扰能力,膜厚越小,受扰动后震荡频率越大且恢复至稳定状态的时间越长;发生端面冲击时膜厚振动频率显著大于全液膜状态下所受扰动情况。随转速及密封腔压力变化值的不断扩大,接触载荷值及冲击频率均不断增大,冲力响应越显著,在端面接触发生瞬间有明显的速度方向突变。

Dynamic analysis for vibration and impact of liquid film sealing

The instantaneous change of operating conditions, system vibration and insufficient lubrication easily cause rub-impact of sealing surface, which has serious effect on the service life of liquid film seals. Dynamic model of sealing system considering face contact was established. Then the equations of motion, Reynolds equation considering mass conservation cavitation boundary condition and asperity contact equation were solved simultaneously at each time step. Furthermore, the effects of liquid film cavitation, axial disturbance and transient operating conditions on seal stability and impact characteristics were investigated. Results show that cavitation dramatically improves the anti-disturbance ability of sealing system. The vibration frequency of liquid film is significantly larger than that of full film lubricated regime when contact occurs. The impact force and shock frequency are continuously enhanced with increase of speed and pressure. There is an obvious change of velocity direction at the instant of face impact.